Despite the efforts of health care practitioners, medical errors are inevitable. Disclosure of errors is patients’ demand and right. The aim of this study was to determine the nursing staff’s attitudes about disclosure of medical errors to patients and its relationship with disclosure of actual and hypothetical errors. In this descriptive cross-sectional study, 180 of the nursing staff employed in the educational hospitals of the city of Khorramabad were selected by non-probability quota and available sampling. Data collection tools were a valid and reliable questionnaire including some questions about the nursing staff’s attitude toward disclosing medical errors to patients, recording and reporting actual errors, and scenarios to investigate the tendency of nurses for reporting hypothetical errors. The data was analyzed SPSS software. The findings indicate that the mean score of the nursing staff’s attitude about disclosing medical errors to patients was 80.50 14.4. The mean score of the nursing staff’s attitudes toward recording minor actual errors (P < 0.02) and their tendency to disclose hypothetical errors causing minor injuries (P < 0.001), moderate injuries (P < 0.001) and major injuries (P < 0.003) were meaningfully more than those who did not tend to disclose errors. There was no significant difference between attitudes of nurses with a history of disclosing actual errors that lead to major harms to patients (P = 0.64) and those who did not report such medical errors to patients. Attitude of the nursing staff toward disclosing medical errors to patients was at a moderate level, which practically increases the probability of concealing errors.